fix: mujoco not found in make commands

Author: juelg

cmake/FindMuJoCo.cmake

@@ -7,8 +7,22 @@ if (NOT MuJoCo_FOUND)
         return()
     endif()
 
-    # Check if the include directory exists
-    cmake_path(APPEND Python3_SITELIB mujoco include OUTPUT_VARIABLE MuJoCo_INCLUDE_DIRS)
+    # Get MuJoCo path from python
+    execute_process(
+        COMMAND ${Python3_EXECUTABLE} -c "import mujoco; print(mujoco.__path__[0])"
+        OUTPUT_VARIABLE MUJOCO_PATH
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+
+    if (NOT MUJOCO_PATH)
+        set(MuJoCo_FOUND FALSE)
+        if (MuJoCo_FIND_REQUIRED)
+            message(FATAL_ERROR "Could not find MuJoCo. Please install MuJoCo using pip.")
+        endif()
+        return()
+    endif()
+
+    set(MuJoCo_INCLUDE_DIRS "${MUJOCO_PATH}/include")
     if (NOT EXISTS ${MuJoCo_INCLUDE_DIRS})
         set(MuJoCo_FOUND FALSE)
         if (MuJoCo_FIND_REQUIRED)
@@ -17,9 +31,7 @@ if (NOT MuJoCo_FOUND)
         return()
     endif()
 
-    # Check if the library file exists
-    cmake_path(APPEND Python3_SITELIB mujoco OUTPUT_VARIABLE mujoco_library_path)
-    file(GLOB mujoco_library_path "${mujoco_library_path}/libmujoco.so.*")
+    file(GLOB mujoco_library_path "${MUJOCO_PATH}/libmujoco.so.*")
     if (NOT mujoco_library_path)
         set(MuJoCo_FOUND FALSE)
         if (MuJoCo_FIND_REQUIRED)